Anthony writes:

When I saw the announcement, I didn’t know quite what to expect.  I’d heard LG here and there over the past year and there was a tendency to a lack of focus.  On TWiV, we had the opportunity to hear the author of The Coming Plague after a quarter century of increased sophistication.  You deserve credit for creating the environment that allowed that expertise to bloom,


PS Should that be SARS CoV 2 variant?

Greg writes:

Hi TWIV Team,

Thanks for all your great work throughout the pandemic.

My wife and I have young kids, and from time to time, we need to administer COVID tests for them in order to satisfy preschool requirements. Nowadays, antigen tests are available from the corner drug store, and we’ve used Abbott BinaxNOW a few times and have greatly appreciated the convenience of it.

The BinaxNOW test prescribes inserting a swab into the nose for sample collection. While this is way better than a nasopharyngeal swab (which our kids have been subjected to and was *highly unpleasant* for all involved), it’s still not a popular proposition. Mouth swabs, however, are no big deal for them, and they happily comply.

My understanding is that mouth swabs have been shown to be as effective (or nearly as effective) as nose swabs, and only slightly less effective as nasopharyngeal swabs, at detecting SARS-CoV-2. However, I believe those studies were done with PCR tests. 

Would you expect similar conclusions to apply to an antigen test? 

I understand that your answer is likely to only be speculation and not an endorsement of testing outside of the written instructions.


Pittsburgh, PA

Lexie writes:

Hey guys, 

I love the show (especially the weather and the banter!).  Thank you so much for what you do! I’m not a scientist at all, but I want to be a science-conscious parent/teacher and you guys have kept me sane all year by helping me understand how to wade through the mess of science journalism during a pandemic.  

My question is: I’ve heard here and there that maybe the best thing for people who got the J&J vaccine is to get a Pfizer booster to protect better from the Delta variant. What do you think about this?  My parents (including my anti-mask mom) are supposed to visit in a couple weeks because they got their shots but they got the J&J. I’ve been so strict this entire time not letting anyone visit and not taking my kids out – it’s caused a lot of tension with aforementioned grandma.  My children were both very premature and I take their health – especially pulmonary health – very seriously.  Should I not let them come? Should I tell them to get a Pfizer before they come? Or is it not a big deal?  I don’t want to make decisions on emotion, but I also want to make safe decisions when it comes to my kids. 

Our case rate here is very low but I worry my mom is probably traveling a lot and could pick up this Delta variant and bring it here (we live states away from them).  

Unrelated to that question, I wanted to say our family is participating in an NIH study where we regularly test for COVID. The study is for families with preschoolers to see who in the family tends to get COVID first and how it is passed through the family. It’s fascinating stuff and I hope it helps us have better data on kids before they start school again in the fall. I hope we get the results broken down in a TWIV episode when it’s done! Maybe then I’ll understand what we are doing! (Only sort of kidding…) 

Don’t get me started on this anti-mask stuff. It’s making me insane.  Thank god YOU all bring me back to sanity! 

– Lexie 

Kevin writes:

Hi TWiVers,

What do you think about heterologous vaccine regimens (i.e., “mixing and matching”)? I’m especially curious about the use of mRNA vaccines as “boosters” for people who have already received a viral vector vaccine. 

The NIH is running a clinical trial of mixed vaccine schedules but, anecdotally, it seems like people who received J&J have already begun to seek out “boosters” on their own. 

So what do we know about the interaction between different vaccines and “variants of concern”? Is there a risk that J&J recipients will become asymptomatic spreaders? And if vaccines are available locally, is it wasteful or harmful for a person who previously received J&J to get a dose of an mRNA vaccine?

Here’s an announcement of the NIH study: 

And here are two Twitter threads that seem to have kicked off coverage in the popular press:

– June 21, Dr. Michael Lin, neurobiologist at Stanford, tweeted that the CDC should allow J&J recipients to get an mRNA booster:

– June 22, Dr. Angela Rasmussen, virologist at the U of Saskatchewan, reported receiving a single dose of Pfizer to “top off” the J&J shot she received in April:

Thanks for considering these questions. And thank you for all of your work on the podcast. 



Melanie writes:

Dear TWIV team,

Thank you for illuminating us on all-things viral. I have been listening since the early days of the pandemic and have always appreciated your coverage and insights. I am one of the unlucky few (well, 9 million!) who received the J&J vaccine here in the US, which is believed to have lower efficacy against the Delta variant. I have two questions: 

1. I agreed to get the J&J vaccine on the premise that the clinical trials for that vaccine included greater diversity of participants, and in the presence of some early variants, whereas Moderna/Pfizer trials took place with healthier cohorts earlier in the pandemic. As such, the true comparative efficacy of these vaccines is not known.  Would you agree with this reasoning? Or have there been further studies showing Moderna/Pfizer’s effectiveness in less healthy subjects/in the presence of variants? (What I am interested in is preventing illness. I understand all these vaccines have been good at protecting against hospitalization/death.)  TL;DR: Is J&J definitely less effective at preventing illness?

2. I would like to get a Moderna or Pfizer booster shot in the coming few weeks, before the CDC completes its studies. I cannot find any literature commenting on what complication might arise from taking an mRNA vaccine after an adenovirus vaccine. Do you know what complications they might be concerned about? It seems logical that there would be no problem, and indeed Canada and parts of the EU have approved mixing vaccine types. As the Delta variant rapidly spreads in the US, and with myself home with an infant (but soon to return to a very busy college campus for work), I’d like to get an mRNA booster. Is there any real reason to wait?

Thank you for your time. I so appreciate you all!


Dhruti writes:

Dear TWIV team, 

It was a very nice discussion of gut translocation in children with MIS in covid19 infection. 

For adults in covid ICU we have seen many cases of blood stream infection where we thought the source could only be from the gut. During covid pandemic in India infection control practices were down into the drain. We did extensive environmental surveillance so that we can rule out infection occurring due to contaminated invasive lines. 

I like what Dr Kathy Spindler said gut translocation must be present but it may be under the radar. 

Thanks for discussing this amazing paper.